The invention relates to a fuel cell arrangement including a fuel cell current source, peripheral units and a controlled hydrogen source associated to the fuel cell current source, based on the hydrolysis of a hydride, and furthermore including an electronic control circuit for controlling the fuel cell current source, this circuit exhibiting at least one terminal for an operational signal, and including an electronic control circuit for controlling the hydrogen source, this circuit exhibiting at least one input terminal for an operational signal of the control circuit of the fuel cell current source and at least one output terminal connected to the hydrogen source for control signals with the help of which the operational state of the hydrogen source can be influenced; the invention relates furthermore to a method for the operation of the fuel cell arrangement.
The fuel cell arrangements to which the invention relates can consist of one or several fuel cells, in particular connected in series in the form of a fuel cell stack, with peripheral units such as valves, fans, control means for influencing the output power etc. For their operation gaseous hydrogen is required.
It is known per se to use hydroborons as hydrogen source, wherein metal ions serve for charge compensation. The best known hydride used for this purpose is sodium borohydride NaBH4; it is, however, also possible to use LiBH4, Al(BH4)3, Mg(BH4)2 etc. These substances can be used dissolved in aqueous, preferably slightly alkaline solution, but also in other suitable solvents. The hydrolysis of the hydride is started by the presence of a catalyst or by an acid medium. In this connection reference is made to the article by Schlesinger et al. “Sodiumborohydride, its Hydrolysis and its Use as a Reducing Agent and in the Generation of Hydrogen”, in J. Am. Chem. Soc. 1953, 75, 215–219. It is also known to use such substances as hydrogen source for fuel cells.
For generating gas from a liquid as a result of a catalytic reaction, it is further known to control the reaction by means of the gas pressure above the liquid level and the thus resulting displacement of liquid away from the catalyst into vessel departments with lower gas pressure. In this way, the liquid is displaced from the area of a catalyst bed by means of the pressure of the generated gas if the gas is not required and thus not discharged; afterwards, when the gas is discharged, the liquid returns and gets again into contact with the catalyst bed. Such a control system, however, is relatively sluggish and insensitive to various reaction parameters which have an influence on the operation.
Such reaction parameters which have an influence on the reaction speed are e.g. the temperature and the state of the solution. The amount of catalyst and the size of the reaction space have to be adapted to the most unfavourable conditions. However, this can lead to a non-controllable over-production in the case of favourable conditions, i.e. a to high reaction speed.
Advantageously, both the fuel cell current source and the hydrogen source are controlled by means of electronic control circuits. The current source provides a current adjusting itself, supplied to a load such as an incandescent lamp, or e.g. for the operation of a vehicle it gets a power demand signal by a control measure of the vehicle operator. The gas generation in the hydrogen source has to be timely adapted to the fuel requirements of the current source and consequently has to follow it in the case of changes.